JPH0968709A - Rubbing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of the transfer and C2 orientation of liquid crystal molecules and to improve the yield. SOLUTION: The feed speed (v) of a conveyor 13 is continuously increased from the start of rubbing (the time when the rubbing is started by contact of a rubbing roller 11 with the front end edge of a substrate E) to the end of the rubbing (the time when the rubbing roller 11 parts from the rear end edge of the substrate E) at the time of subjecting one sheet of the substrate E to a rubbing treatment. Such control of the feed speed (v) is executed similarly for the respective substrates E. The other rubbing conditions (roller rotating speed R, indenting rate (x), etc.) are held at desired values. As a result, the adequate range of the rubbing conditions is widened and the occurrence of the transfer and C2 orientation of the liquid crystal molecules is prevented even if the indenting rate (x) and the roller rotating speed R deviate slightly from the desired values.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubbing method for improving the manufacturing yield by preventing the movement phenomenon of liquid crystal molecules and the occurrence of C2 orientation.

[0002]

2. Description of the Related Art In recent years, display devices of the type in which transmitted light rays are controlled by using a chiral smectic liquid crystal, particularly a ferroelectric liquid crystal, in combination with a polarizing element to control transmitted light rays are Clark and Lagerwal.
11) (Japanese Patent Laid-Open No. 56-10721).
No. 6, the specification of US Pat. No. 4,367,924).

This ferroelectric liquid crystal generally has a non-helical chiral smectic C phase (SmC ^* ) or H phase (SmH ^* ) in a specific temperature range, and responds to an electric field applied in this state. Has either a first optical stable state or a second optical stable state, and has the property of maintaining that state when no electric field is applied, that is, bistability, and is resistant to changes in the electric field. It responds quickly and is expected to be widely used for high-speed and memory type display devices.

[0004]

By the way, in the above-mentioned ferroelectric liquid crystal display element, a rubbing treatment is performed in the manufacturing process to give a pretilt angle. The problem of movement occurred, and conversely, the problem of occurrence of C2 orientation occurred when the pretilt angle was small (details will be described later). Therefore, in order to avoid such a problem, it is necessary to control the rubbing condition so that the pretilt angle falls within an appropriate range. However, in practice, since the proper range of the rubbing condition is narrow, the rubbing condition is likely to deviate from the proper range, liquid crystal molecules move or C2 alignment occurs, and the manufacturing yield of the liquid crystal display element is reduced. .

Here, movement of liquid crystal molecules and C2 orientation will be described. <Movement of Liquid Crystal Molecules> First, the movement phenomenon of liquid crystal molecules will be described with reference to FIG.

Ferroelectric liquid crystal molecules have bistability as described above, and the average molecular position in this bistable state (hereinafter referred to as "average molecular axis direction") is designated by reference numeral 21 in FIG. , 21 '. In addition, reference numeral 20 in the drawing
Indicates the rubbing direction.

Now, for example, the average molecular axis direction is 21.
When an AC electric field 22 that does not cause switching is applied and the ferroelectric liquid crystal display element is driven for a long time, the liquid crystal molecules move in the direction of arrow a, the cell thickness at the cell end B increases, and the average molecular weight increases. When an alternating electric field 22 'is applied so that the axial direction becomes 21' and is not switched, the liquid crystal molecules move in the direction of arrow b and the cell thickness of the C portion increases. Then, there is a problem that the portion where the cell thickness is increased appears yellow (hereinafter referred to as "yellowing").

Here, the moving directions a and b of the liquid crystal molecules are defined by the rubbing direction 20 and the average molecular axis directions 21, .... This has been confirmed by the present inventors through experiments. The liquid crystal molecules move in a direction perpendicular to the rubbing direction 20, and the liquid crystal moves in the smectic layer.

The inventor of the present invention speculates that the cause of the movement of the liquid crystal molecules is due to the electrodynamic effect generated by the fluctuation of the dipole moment of the liquid crystal molecules in the AC electric field due to the driving pulse. ing.

Since the moving direction of the liquid crystal molecules depends on the rubbing direction as described above, it is easily inferred that the yellowing phenomenon depends on the pretilt state at the substrate interface. Specifically, when the pretilt angle is large, liquid crystal molecules move to cause a yellowing phenomenon.

In general, yellowing is noticeably observed near the liquid crystal injection port. In addition, here, the case where a liquid crystal material in which the direction of spontaneous polarization is negative is described, and when the spontaneous polarization is reversed, the moving directions of the liquid crystal molecules are also reversed. Furthermore, the moving direction of the liquid crystal molecules changes depending on the state of the substrate interface, and the amount of moving liquid crystal molecules decreases. <C2 Alignment> Next, the C2 alignment will be described with reference to FIGS. 2 and 3.

First, two kinds of orientation states, C1 and C2, will be explained by the difference in chevron structure of the smectic layer as shown in FIG. Here, reference numeral 31 in FIG. 2 indicates a smectic layer, reference numeral 32 indicates a C1 orientation region, and reference numeral 33 indicates C.
Two orientation regions are shown respectively.

Smectic liquid crystals generally have a layered structure, but when the SmA phase transitions to the SmC phase or the SmC ^* phase, the layer spacing shrinks. As shown in FIG. It takes a bent structure (chevron structure) in the vicinity. Here, as shown in FIG. 2, there may be two bending directions C1 and C2, but as is well known, uniaxial alignment (rubbing) causes liquid crystal molecules at the interface of the substrate to form an angle with the substrate. (Pretilt),
The direction is the direction in which the liquid crystal molecules lift their heads toward the rubbing direction 20 (the tip becomes floating). Due to this pretilt, the C1 orientation and the C2 orientation are not elastically energy-equivalent, and a transition may occur at a certain temperature. In addition, mechanical strain may cause dislocation. When the layered structure of FIG. 2 is viewed in a plan view, the boundary 34 at the time of shifting from the C1 orientation to the C2 orientation in the rubbing direction 20 is zigzag lightning and is called a lightning defect, and the boundary 34 at the time of shifting from the C2 orientation to the C1 orientation. The boundary 35 has a wide and gentle curved shape and is called a hairpin defect.

The ferroelectric liquid crystal display element comprises a pair of substrates arranged in parallel, and the surfaces of these substrates are subjected to a uniaxial alignment treatment in the same direction to align the ferroelectric liquid crystal. However, the pretilt angle of the ferroelectric liquid crystal is α, and the tilt angle (1/2 of the cone angle) is Θ,
When the ferroelectric liquid crystal is oriented so as to satisfy the following equation, where the inclination angle of the SmC ^* layer is δ, there are four states having a chevron structure in the C1 orientation state.

[0015]

[Formula 3] Θ <α + δ These four C1 orientation states are different from the conventional C1 orientation states. Among them, two of the four C1 orientation states form a bistable state (uniform state). are doing. Here, if the apparent tilt angle when there is no electric field is θa, of the four states in the C1 orientation state, the state showing the relationship of the following equation is called the uniform state.

[0016]

[Formula 4] Θ>θa> Θ / 2 In this uniform state, it is considered that liquid crystal molecules (directors) are not twisted between the upper and lower substrates in view of their optical properties. FIG. 3A is a schematic view showing the arrangement of directors at respective positions between the substrates in each state of C1 orientation. In the figure, reference numerals 51 to 54 show the state in which the director is projected on the bottom surface of the cone in each state and viewed from the bottom surface direction, which is called a C director. In this figure, reference numeral 5
Reference numerals 1 and 52 are C-director arrangements which are considered to be in a spray state and reference numerals 53 and 54 are considered to be in a uniform state. As you can see from the figure, two uniform states 53
In Nos. 54 and 54, the positions of the liquid crystal molecules at the interface between the upper and lower substrates are replaced with the positions in the splay state. FIG.
(b) shows the C2 orientation, and there are two states 55 and 56 due to internal switching without switching at the interface.

This C1 orientation uniform state produces a larger tilt angle θa than the conventionally used bistable state in the C2 orientation, and has a large luminance and a high contrast.

By the way, when a ferroelectric liquid crystal display element having a small pretilt angle is driven at a low temperature, a C2 alignment state may be partially generated (for example, on the side opposite to the liquid crystal injection port) during the C1 alignment. . Further, there is a problem that a zigzag defect occurs due to the occurrence of the C2 orientation state, and the image quality is partially deteriorated.

The cause of the C2 orientation state is that the "SmC ^* layer inclination angle δ" becomes smaller with a decrease in temperature, the pretilt angle α is low, the auxiliary electrode (metal electrode), etc. Due to. Therefore, such C2
In order to prevent the occurrence of the alignment state, the pretilt angle α may be increased.

Therefore, in order to prevent the above-mentioned yellowing phenomenon and the occurrence of C2 orientation, it is necessary to control the rubbing conditions such as the pressing amount x and the rotation speed R of the roller so that the pretilt angle is in an appropriate range. is there. But,
In practice, since the proper range of the rubbing condition is narrow, the rubbing condition is likely to deviate from the proper range, liquid crystal molecules move or C2 alignment occurs, and the manufacturing yield of the liquid crystal display element is reduced.

Therefore, it is an object of the present invention to provide a rubbing method capable of preventing the occurrence of alignment defects and yellowing and improving the manufacturing yield.

[0022]

The present invention has been made in view of the above circumstances, and is used for manufacturing a liquid crystal element in which a chiral smectic liquid crystal is sandwiched between a pair of substrates, and at least one of the substrates is provided. In a rubbing method in which an alignment control force is applied by rubbing a rubbing cloth, the rubbing strength is continuously reduced in the one substrate. In this case, a rubbing device including a rubbing roller to which the rubbing cloth is attached, a rotation driving unit that rotationally drives the rubbing roller, and a moving unit that relatively moves the rubbing roller and the one substrate are provided. Using the rubbing cloth in contact with the one substrate, the rubbing roller is driven to rotate, and the rubbing roller and the one substrate are moved relatively to each other. The orientation regulating force may be applied to the.

Further, the relative moving speed of the rubbing roller and the one substrate may be continuously increased, and the rubbing strength may be changed based on the increase of the relative moving speed. Further, the rotation speed of the rubbing roller may be continuously decreased, and the rubbing strength may be changed based on the decrease in the rotation speed. Furthermore, the contact pressure of the rubbing cloth with respect to the one substrate may be continuously decreased, and the rubbing strength may be changed based on the decrease of the contact pressure.

Further, the chiral smectic liquid crystal is
Θa, which is at least two stable states, and is ½ of the angle formed by these optical axes, and the cone angle Θ are

[0025]

[Formula 5] It is preferable to satisfy the relation of Θ> θa> Θ / 2.

Furthermore, the pretilt angle of the liquid crystal is α, the cone angle is Θ, and the tilt angle of the chiral smectic layer is δ.
And if

[0027]

[Expression 6] α> Θ−δ may be satisfied.

Furthermore, the liquid crystal element may have a transparent electrode formed on the substrate and a metal electrode formed on these transparent electrodes.

Based on the above construction, when rubbing cloth is rubbed against the substrate to give the alignment regulating force, if the rubbing strength is continuously decreased in the substrate, even if the rubbing condition is slightly deviated, It is possible to prevent the occurrence of deformation and the occurrence of C2 orientation.

[0030]

Embodiments of the present invention will be described below with reference to the drawings.

First, the first embodiment will be described with reference to FIGS. 4 and 5.

FIG. 4 is a cross-sectional view schematically showing the structure of the ferroelectric liquid crystal display element. The liquid crystal display element P is composed of two glass substrates 1a and 1b (hereinafter, referred to as appropriate). Upper substrate 1a "and" lower substrate 1b "), and transparent electrodes 2a, 2 are provided on these substrates 1a, 1b.
b and insulating films 3a and 3b for covering the transparent electrodes 2a and 2b
And the orientation control films 5a and 5b covering the insulating films 3a and 3b.
Are formed in order. Here, the thickness of the transparent electrodes 2a and 2b is about 40 to 300 nm, and the thickness of the insulating films 3a and 3b is 10 to 300 nm. The insulating films 3a and 3b are formed by coating and baking, but may have a multilayer structure with a sputtered film. The thickness of the orientation control films 5a and 5b is 5 to 30 nm, and the surfaces of the orientation control films 5a and 5b are uniaxially oriented.

On the other hand, a large number of spacers 7, ...
Are arranged to define the substrate gap, and the glass substrate 1
The ends of a and 1b are bonded by a seal member (not shown). Further, a ferroelectric liquid crystal, preferably, a ferroelectric liquid crystal 9 having at least two stable states is arranged in the gap.

In the present embodiment, the ferroelectric liquid crystal 9 may be in the chiral smectic phase state, specifically, the chiral smectic C phase (SmC ^* ) and H phase (SmH ^* ). , Phase I (SmI ^* ),
Liquid crystals of K phase (SmK ^* ) or G phase (SmG ^* ) can be used.

Particularly preferred liquid crystals include those exhibiting a cholesteric phase on the higher temperature side, for example, pyrimidine-based mixed liquid crystals exhibiting the following phase transition temperatures and physical properties.

[0036]

Embedded image Pyrimidine type liquid crystal A −3 ° C. 57 ° C. 79 ° C. 85 ° C. Cryst → SmC ^* → SmA → Ch → Iso Tilt angle Θ = 14 ° (30 ° C.) Layer tilt angle δ = 11 ° (30 ° C.) Apparent Tilt angle θ = 11 ° (30 ° C.) In the present embodiment, the liquid crystal 9 exhibits at least two stable states, and θa which is 1/2 of the angle formed by the optical axes thereof. The cone angle Θ is

[0037]

[Formula 7] The relation of Θ>θa> Θ / 2 is satisfied. When the pretilt angle of the liquid crystal 9 is α, the cone angle is Θ, and the tilt angle of the chiral smectic layer is δ,

[0038]

[Expression 8] α> Θ−δ is satisfied.

Next, the rubbing method used in this embodiment will be described.

A rubbing apparatus 10 as shown in FIG. 5 is used for the rubbing process. This rubbing device 10 is
A rubbing roller 11 rotatably supported is provided, and a rubbing cloth 12 is attached to the outer peripheral surface of the roller 11. Further, the roller 11 is connected to a motor (rotational driving means) M and is configured to be rotationally driven at a predetermined rotational speed R. Furthermore, this roller 1
A conveyor (moving means) 13 is arranged below 1 so that the substrate E placed on the conveyor 13 is moved at a predetermined relative moving speed v (hereinafter, referred to as “feeding speed v”). It has become. Furthermore, the rubbing roller 11
Adjust the height position and push in x (contact pressure)
Is configured to be variable.

In this embodiment, the feed rate v is
When rubbing one substrate E, from the start of rubbing (when the rubbing roller 11 contacts the leading edge of the substrate E to start rubbing) to the end of rubbing (from the rear edge of the substrate E to the rubbing roller 11). It is configured such that the rubbing strength is continuously reduced by increasing the rubbing strength. Then, such control of the feed speed v is similarly performed for each substrate. During this period, the roller rotation speed R is constant (for example,
1000 rpm) and the pushing amount x is kept constant (for example, 0.15 mm).

Next, the effect of the present embodiment will be described.

According to the present embodiment, the rubbing condition is widened by continuously increasing the feed speed v, and even if the pushing amount x and the roller rotation speed R are slightly deviated from desired values, yellowing or C2 orientation is caused. Can be prevented. Therefore, the manufacturing yield of the liquid crystal display element P is improved, and as a result, the cost of the liquid crystal display element P is reduced.

The present inventor conducted an experiment to confirm the effect of this embodiment. Hereinafter, the contents of the experiment will be described. <Experiment 1> The glass substrates 1a and 1b used in this experiment have a thickness of 1.1 mm, and the transparent electrodes 2a and 2b have a thickness of about 1 mm.
An ITO film having a thickness of 50 nm was used.

A spin coating method was used to form the orientation control films 5a and 5b. That is, the solution (NMP / nBC = 1/1 1.5 wt% solution of LQ1802 manufactured by Hitachi Chemical Co., Ltd.) was dripped on the glass substrates 1a and 1b rotating at a speed of 2000 rpm, and was rotated for 20 seconds. . After that, heat baking treatment was performed at a temperature of 270 ° C. for about 1 hour. The film thickness of the orientation control films 5a and 5b formed by this method was 20 nm.

Next, the orientation control films 5a and 5b thus formed were unidirectionally rubbed with a nylon flocked cloth. In this experiment, one substrate E
When rubbing, the feeding speed v is continuously increased from 20 mm / s to 40 mm / s from the start of rubbing to the end of rubbing. Further, the roller rotation speed R is constant (1000 rpm), and the pushing amount x is constant (details will be described later).

Then, on one of the glass substrates 1a or 1b, alumina beads (average particle size: 1.1 μm) as spacers 7, ... Are scattered, and the two glass substrates 1a and 1b are bonded together to form a cell. did. The glass substrate 1a,
In the state in which 1b is bonded, the rubbing treatment axes are parallel in a side view and are in a plan view (the upper substrate 1
(when viewed from the a side), the rubbing treatment axis on the lower substrate 1b side is set to a position rotated by 8 ° in the clockwise direction from the rubbing treatment axis on the upper substrate 1a side.

Then, a mixed liquid crystal A containing a pyrimidine-based liquid crystal as a main component was vacuum-injected in an isotropic phase, and then 0.5 ° C. /
Orientation was achieved by slow cooling to room temperature at a cooling rate of min.

In this experiment, a plurality of liquid crystal display elements P having different pushing amounts x,
…made. That is, the pressing amount x is constant for one liquid crystal display element P (upper and lower substrates 1a and 1b), but is different by 0.02 mm in the range of 0.17 mm to 0.25 mm between the liquid crystal display elements. It was

Then, with respect to the produced liquid crystal display elements P, ..., The amount of increase in cell thickness and the occurrence of C2 orientation were examined. Table 1 shows the results.

[0051]

[Table 1] According to this experiment, the pushing amount x is 0.17 to 0.25 mm.
It was confirmed that the cell thickness did not increase and the C2 orientation did not occur within the range.

The occurrence of C2 orientation was observed by driving the liquid crystal display element P at a temperature of 5 ° C. The increase in cell thickness was measured by the following method.

That is, when measuring the cell thickness, the glass substrates 1a and 1b had a size of 75 mm × 75 mm.
Then, the cell thickness of the regions A, B, C, D shown in FIG. 1 was measured. Next, the write waveforms 22 and 22 'shown in FIG. 1 were input to the liquid crystal display element P. The write waveforms 22 and 22 'had a pulse width of 30 μS, a 1/3 bias, and a 1/1000 duty. When such write waveforms 22 and 22 'are input, the average molecular axis of the liquid crystal molecule becomes reference numeral 21 or 21' as described above. In this state, continuous writing was performed for 7 days, and after driving, the cell thicknesses of the regions A, B, C and D were measured again. <Experiment 2> In this experiment, the feed speed v was not changed as in Experiment 1 and was constant at 30 mm / s, and the rotation speed R of the rubbing roller was constant at 1000 rpm.

The other conditions were the same as in Experiment 1 above, and a plurality of liquid crystal display elements having different indentations x within the range of 0.17 mm to 0.25 mm were prepared to increase the cell thickness and the C2 orientation. Occurrence and investigation. The results are shown in Table 2.

[0055]

[Table 2] According to this experiment, the proper range of the pushing amount x (the range where the cell thickness does not increase and the C2 orientation does not occur) is 0.21 mm,
It was confirmed that it was considerably narrower than that in Experiment 1.

Now, comparing Experiment 1 and Experiment 2,
It can be understood that by continuously increasing the feed rate v, the appropriate range of the pushing amount x is expanded, and even if the pushing amount x deviates from the desired value to some extent, yellowing or C2 orientation is prevented.

Next, a second embodiment of the present invention will be described.

In this embodiment, the feed speed v is constant (for example, 30 mm / s) and the pushing amount x is constant (for example, 0.15 mm). Further, the roller rotation speed R is continuously reduced when rubbing one substrate E from the start of rubbing to the end of rubbing, whereby the rubbing strength is continuously reduced. .

Next, the effect of the present embodiment will be described.

According to the present embodiment, the roller rotation speed R
By continuously decreasing the value, the rubbing condition spreads, and even if the rubbing condition such as the pushing amount x deviates from a desired value to some extent, it is possible to prevent yellowing and C2 orientation from occurring. Therefore, the manufacturing yield of the liquid crystal display element P is improved, and as a result, the cost of the liquid crystal display element P is reduced.

The present inventor conducted an experiment to confirm the effect of the present embodiment. Hereinafter, the contents of the experiment will be described. <Experiment 3> In this experiment, when rubbing one substrate E, the roller rotation speed R was continuously reduced from 1200 rpm to 800 rpm from the start of rubbing to the end of rubbing. On the other hand, the feed speed v is 30
The condition was the same as in Experiment 1 above, except that the value was constant at mm / s.

The pushing amount x is 0.17 mm to 0.
Create different liquid crystal display elements within the range of 25 mm,
The increase in cell thickness and the occurrence of C2 orientation were investigated. Table 3 shows the results.

[0063]

[Table 3] According to this experiment, the pushing amount x is 0.15 to 0.23 mm
It was confirmed that the cell thickness did not increase and the C2 orientation did not occur within the range. <Experiment 4> In this experiment, the roller rotation speed R was not changed as in Experiment 1 and was kept constant at 1000 rpm.

The other conditions were the same as in Experiment 1 above, and a plurality of liquid crystal display devices having different indentations x within the range of 0.17 mm to 0.25 mm were prepared, and the increase in cell thickness and the C2 orientation were determined. Occurrence and investigation. The results are shown in Table 4.

[0065]

[Table 4] According to this experiment, the proper range of the pushing amount x (the range where the cell thickness does not increase and the C2 orientation does not occur) is 0.21 mm,
It was confirmed that it was considerably narrower than that in Experiment 1.

Here, comparing Experiment 3 and Experiment 4,
It can be understood that by continuously decreasing the roller rotation speed R, the appropriate range of the pushing amount x is expanded, and even if the pushing amount x deviates from the desired value to some extent, the occurrence of yellowing or C2 orientation is prevented.

Next, a third embodiment of the present invention will be described.

In this embodiment, the feed speed v is constant (for example, 20 mm / s) and the roller rotation speed R is constant (for example, 1000 rpm). Further, the conveyor 13 is installed with a slight inclination, and as a result, the pushing amount x decreases continuously when rubbing one substrate E from the start of rubbing to the end of rubbing.
Thereby, the rubbing strength is continuously reduced.

Next, the effect of this embodiment will be described.

According to the present embodiment, the rubbing condition is expanded by continuously decreasing the pushing amount x,
Even if the rubbing conditions such as the feeding speed v are slightly deviated from desired values, it is possible to prevent yellowing and C2 orientation from occurring. Therefore,
The manufacturing yield of the liquid crystal display element P is improved, and as a result, the cost of the liquid crystal display element P is reduced.

The present inventor conducted an experiment to confirm the effect of the present embodiment. Hereinafter, the contents of the experiment will be described. <Experiment 5> In this experiment, when rubbing one substrate E, the pushing amount x is continuously reduced from 0.25 mm to 0.15 mm from the start of rubbing to the end of rubbing. On the other hand, the roller rotation speed R is 1000
The rpm was kept constant, and the other conditions were the same as in Experiment 1 above.

A plurality of liquid crystal display elements having different feed rates v in the range of 20 to 40 mm / s were prepared, and the increase in cell thickness and the occurrence of C2 orientation were investigated. The results are shown in Table 5.

[0073]

[Table 5] According to the present embodiment, it was confirmed that if the feed rate v is in the range of 20 to 36 mm / s, the cell thickness does not increase and the C2 orientation does not occur. <Experiment 6> In this experiment, the pushing amount x is the same as in Experiment 1.
It was not changed and was kept constant at 0.2 mm.

Other conditions were the same as in Experiment 1 above, and a plurality of liquid crystal display elements having different feed rates v in the range of 20 to 40 mm / s were prepared, and the increase in cell thickness and the occurrence of C2 alignment were generated. Examined. Table 6 shows the results.

[0075]

[Table 6] According to this experiment, it was confirmed that the proper range of the feed rate v (the range in which the cell thickness does not increase and the C2 orientation does not occur) is 20 to 28 mm / s, which is narrower than that in the experiment 1.

Here, comparing Experiment 5 and Experiment 6,
It can be understood that by continuously decreasing the pushing amount x, the proper range of the feed speed v is widened, and even if the feed speed v is slightly deviated from the desired value, yellowing and C2 orientation are prevented from occurring.

Finally, a method of measuring the pretilt angle α will be described.

The pretilt angle α is determined according to Jpn. J. App
l. Phys. Vol. 119 (1980) No. 1
0. It was determined according to the method (crystal rotation method) described in Short Notes 2013. The measurement cell was prepared by laminating two substrates so that the liquid crystal tilts at the upper and lower interfaces were parallel and in the same direction. Further, as a liquid crystal for measuring the pretilt angle, a ferroelectric liquid crystal CS-1014 manufactured by Chisso Corp. was mixed with 20% by weight of a compound represented by the following structural formula as a standard liquid crystal, and the measurement was performed.

[0079]

Embedded image The mixed liquid crystal composition exhibits a SmA phase in the temperature range of 10 to 55 ° C.

The measuring method is as follows: While rotating the liquid crystal cell in a plane perpendicular to the upper and lower substrates and including the alignment treatment axis, the rotation axis is 45 ° with respect to the rotation axis.
The helium-neon laser light with a deflection surface that makes an angle of is irradiated from the direction perpendicular to the rotation axis, and on the opposite side, through the deflection plate with the transmission axis parallel to the incident deflection surface, the transmitted light intensity is increased by the photodiode. It was measured.

The angle formed by the center angle of the hyperbolic group of transmitted light intensity generated by interference and the line perpendicular to the liquid crystal cell is φx.
Then, the pretilt angle α was obtained by substituting in the following equation.

[0082]

[Formula 9] In each of the above-described embodiments, the substrate E is moved and the rubbing roller 11 is rotated at a predetermined stop position. However, the invention is not limited to this, and the substrate E may be stopped. The rubbing roller 11 may be rotated while being moved. Further, both the substrate E and the rubbing roller 11 may be moved.

By the way, in the above-described embodiment, the electrodes are only the transparent electrodes 2a and 2b, and the metal electrodes are not formed, but the metal electrodes are used as auxiliary electrodes.
When it is formed on the surface of 2b, the C2 orientation state is more likely to occur, and therefore it is important to apply this embodiment to remove the C2 orientation state.

[0084]

As described above, according to the present invention,
When rubbing treatment was performed by rubbing a rubbing cloth on the substrate, the rubbing strength was continuously reduced in the substrate. As a result, the proper range of the rubbing conditions is widened, and even if the rubbing conditions such as the pushing amount x deviate from the desired values to some extent, it is possible to prevent the occurrence of yellowing and C2 orientation. Therefore, the manufacturing yield of the liquid crystal element is improved, and as a result, the cost of the liquid crystal element is reduced.

[Brief description of drawings]

FIG. 1 is a diagram for explaining a relationship between a rubbing direction and a liquid crystal moving direction and a method for measuring a cell thickness.

FIG. 2 is a diagram showing an orientation model of a smectic layer.

3A is a schematic view showing the arrangement of directors at respective positions between substrates in each state of C1 orientation, and FIG. 3B is a schematic view showing C2 orientation.

FIG. 4 is a sectional view schematically showing the structure of a liquid crystal display element.

FIG. 5 is a perspective view for explaining the structure and the like of the rubbing device.

[Explanation of symbols]

 1a, 1b Glass substrate (substrate) 2a, 2b Transparent electrode 3a, 3b Insulating film 5a, 5b Alignment control film 9 Ferroelectric liquid crystal 10 Rubbing device 11 Rubbing roller 12 Rubbing cloth 13 Conveyor (moving means) E Substrate M Motor (rotating) Driving means) P liquid crystal display element (liquid crystal element)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuaki Takeda 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Yasushi Asao 3-30-2 Shimomaruko, Ota-ku, Tokyo Kiya Non non corporation

Claims (8)

[Claims] 1. A rubbing method used for manufacturing a liquid crystal device comprising a pair of substrates sandwiching a chiral smectic liquid crystal, wherein a rubbing cloth is rubbed on at least one of the substrates to provide an alignment regulating force. A rubbing method, characterized in that the strength is continuously reduced in the one substrate. 2. A rubbing roller provided with a rubbing roller to which the rubbing cloth is attached, a rotation driving means for rotationally driving the rubbing roller, and a moving means for relatively moving the rubbing roller and the one substrate. Using the device, and with the rubbing cloth in contact with the one substrate,
The rubbing method according to claim 1, wherein the rubbing roller is rotationally driven, and the rubbing roller and the one substrate are moved relatively to each other to impart an alignment regulating force to the one substrate. . 3. The rubbing method according to claim 2, wherein the relative moving speed of the rubbing roller and the one substrate is continuously increased, and the rubbing strength is changed based on the increase of the relative moving speed. . 4. The rotation speed of the rubbing roller is continuously decreased, and the rubbing strength is changed based on the decrease of the rotation speed.
The rubbing method according to claim 2, wherein: 5. The rubbing method according to claim 2, wherein the contact pressure of the rubbing cloth against the one substrate is continuously decreased, and the rubbing strength is changed based on the decrease of the contact pressure. 6. The chiral smectic liquid crystal exhibits at least two stable states, and θa, which is ½ of the angle formed by the optical axes thereof, and the cone angle Θ are expressed by the following formula: Θ> θa The relationship of> Θ / 2 is satisfied, The rubbing method according to claim 1, wherein the rubbing method is satisfied. 7. When the pretilt angle of the liquid crystal is α, the cone angle is Θ, and the tilt angle of the chiral smectic layer is δ, the following equation 2 is satisfied: α> θ−δ The rubbing method according to any one of claims 1 to 6. 8. The liquid crystal element has a transparent electrode formed on the substrate, and a metal electrode formed on these transparent electrodes, according to any one of claims 1 to 7. The rubbing method according to item 1.